A. Field of the Invention
The present invention relates to the attachment of an optical coupler to a circuit board and, more specifically to the piggy back attachment of an optical coupler to another component, such as an integrated circuity (IC) mounted on a circuit board.
B. Discussion of the Related Art
Conventional data buses made from parallel copper wire technology are used pervasively in electronic circuitry intraframe and interframe interconnects. Copper wire does have its practical limits however. With high speed complex signal processing integrated circuits, the copper wire is limited to 10-20 meters for reliable error free data transmission. Moreover, as the speed of signal processing increases and integrated circuits act even faster, copper wire technology can add undesired delays. Optical technology is being increasingly used to overcome these constraints.
Fiber optic transmission lines (also referenced to as fiber optic cable) have several advantages over copper wire, including an often lower power requirement and an enhanced rate of reliable data transfer.
In a typical application, fiber optic connectors require a coupling device to optically couple the fiber optic transmission line with an opto-electric device (OED). The opto-electric device is generally electrically coupled to a driving circuit or other signal processing circuity. This circuity is conventionally mounted on a printed circuit board or ceramic substrate and is connected to the opto-electric device through the use of electronic pathways on the circuit board or substrate.
This general mounting system suffers from a number of problems however. First, the increased data transmission characteristics of the fiber optics cannot be taken full advantage of because the data must first pass from a signal processor such as a microprocessor, memory, driver integrated circuit, or other integrated circuit devices, to the opto-electric device through conventional electrical wiring connections formed on the substrate. Transmission rates are thus inherently slowed by the location of the opto-electric device on the substrate. The delay associated with this type of connection varies depending on the substrate design layout. Second, the use of electrical wiring paths increases the chance that EMF and other electrical noise will be introduced into the signal. Third, the placement of the opto-electric device on the substrate, and goal of minimizing bending of the fiber optics, limits board design.
The present invention overcomes these past problems by mounting an opto-electric device directly on top of, or below, an integrated circuit which is electrically connected to the opto-electric device. The opto-electric device is mounted directly to leads, or bonding pads, of the integrated circuit such that a minimum electrical path exists for transferring information between the integrated circuit and opto-electric device. Thus, the delay associated with the electrical wiring is minimized and unified for given IC/OED combinations, regardless of substrate design.
The integrated circuit is provided with connectors. These connectors can either be formed into the leads, replace a lead, or be attached to a conventional lead. The connectors can be a bonding pad or pin type receiving surface at the integrated circuit. Those of ordinary skill in the art will recognize that this can include any form of connector surface for enabling a bond between two electric conductors. The connector allows the opto-electric device to be mounted on top of the integrated circuit with respect to the substrate or below the substrate underneath the integrated circuit. In mounting the opto-electric device on the integrated circuit in a piggy back or in an opposite side of the substrate arrangement the full capabilities of the opto-electric device can be utilized while interference is reduced, transmission rates maximized and electric wiring pathway delay minimized and unified for given IC/OED packages.
In another embodiment, the opto-electric device can be either hermetically sealed or non-hermetically sealed with the integrated circuit inside a common package. The package, which can be made from a ceramic or resin, can be provided with a heat sink formed therein.
In another embodiment, two or more opto-electric devices can be mounted on an integrated circuit either in the same plane or one on top and one below the integrated circuit, or piggy backed on top of each other on the integrated circuit.
In another embodiment structural support or locating pins are molded into the integrated circuit. These structural supports or locating pins reduce the strain on the opto-electric device and assist in the mounting process.
In another embodiment, an opto-electric device interface adapter is connected to the integrated circuit such that any opto-electric device, or high transmission rate device, regardless of pin configuration can be attached thereto. The opto-electric device interface is provided with grounded and matched impedance sides that abut the integrated circuit and opto-electric device. The opto-electric device interface adapter can permit multiple opto-electric devices to be connected in a variety of positions. The opto-electric device interface adapter can also have a heat sink formed either between the opto-electric device and integrated circuit, on the opto-electric device or to the side. This permits heat buildup to be dissipated so as not to adversely effect the operations of the integrated circuit or the opto-electric device.
As the term is used herein, xe2x80x9cOEDxe2x80x9d or xe2x80x9copto-electric devicexe2x80x9d refers to a device which converts electrical current to light and/or light to electric current. Those of ordinary skill in the art will recognize that many forms of opto-electric devices exist and that other high transmission rate transmitting/receiving devices that do not use fiber optics, but which use signaling paths which exceed the speed of conventional copper bus technology, can be substituted for the opto-electric device. The term xe2x80x9clightxe2x80x9d refers generally to electromagnetic radiation, and preferably those wavelengths of the electromagnetic radiation to which semi-conductive material is, or can be made, sensitive, whether or not such light is actually visible to the human eye. Non-limiting examples of opto-electric devices include lasers (for example double channel, planar buried hetero structure (DC-PHB), buried crescent (BC), distributed feedback (DFB), distributed bragg reflector (DBR), etc.), light emitting diodes (LEDs) (for example, surface emitting LED (SLED), edge emitting LED (ELED), super luminescent diode (SLD), etc.) or photodiodes (P intrinsic, N, referencing the layout of the semiconductor (PIN), avalanche photodiode (APD), etc.).
Those of ordinary skill in the art will appreciate that the specific structure of the opto-electric device does not matter nor does the specific structure of the integrated circuit matter. Rather, the present invention is directed to a novel manner by which an opto-electric device is connected to an integrated circuit to reduce the wiring path between them.
These and other advantages and features of the invention will become more clearly apparent from the following detailed description of the invention, which is provided in connection with the several drawings attached hereto.